1. Field of the Invention
The present invention relates to a fan wheel assembly for connecting multiple hub rings. Particularly, the present invention relates to the fan wheel assembly for coaxially connecting at least three hub rings and fan blades thereof. More particularly, the present invention relates to the fan wheel assembly for hub rings having first-layer fan blades overlapped second-layer and third-layer fan blades along a longitudinal direction.
2. Description of the Related Art
Referring initially to FIGS. 1 and 2, it illustrates a conventional fan wheel structure in accordance with the prior art. Typically, the fan wheel structure is an axial-flow type of a heat-dissipating fan wheel 1. Generally, the fan wheel 1 includes a hub 11, a plurality of fan blades 12 and a rotary shaft 13. The rotary shaft 13 is adapted to freely connect to a motor stator (not shown) for rotational operation. Each of the fan blades 12 tilts on an outer circumference of the hub 11 and is widely used to drive ambient air. And each of the fan blades 12 includes a leading edge 121 and a trailing edge 122 at its opposite sides.
Generally, the fan wheel 1 is made of plastic material molded in a molding assembly (not shown), and embedded a distal end of the rotary shaft 13 which is made of metal material. In pattern-drawing operation, it is risked that the molding assembly may obstruct and limit the pattern for releasing therefrom. In order to avoid obstructing the pattern in the molding assembly, each leading edge 121 of the fan blades 12 is designed not to overlap each corresponding trailing edge 122 of the adjacent fan blades 12 along a reference line identified as “W” extending in a longitudinal direction.
Furthermore, the total air amount driven by the fan wheel 1 is proportional to total number or total blade-surface area of the driving fan blades 12 according to aerodynamics. Therefore, total number or total blade-surface area of the driving fan blades 12 must be increased to enlarge total driven air amount on condition that the obstruction of the molding assembly is overcome in pattern-drawing operation.
Another construction of the conventional fan wheel is disclosed in U.S. Pat. Nos. 6,572,336 and 6,318,964. Turning now to FIGS. 3 and 4, it illustrates another conventional assembled fan wheel structure in accordance with the prior art. Generally, the fan wheel 1′ includes an assembled hub 11′ and a plurality of assembled fan blades 12′. The assembled hub 11′ consists of an upper hub 11a and a lower hub 11b. The upper hub 11a provides with a plurality of upper fan blades 12a while the lower hub 11b providing with a plurality of lower fan blades 12b. Each of the assembled fan blades 12′ consists of the upper fan blade 12a and the lower fan blade 12b, and includes a leading edge 121′ and a trailing edge 122′. By such an assembled relationship, each starting point of the leading edge 121′ of the assembled fan blade 12′ is permitted to overlap each of the adjacent trailing edge 122′ along a reference line identified as “X” extending in a longitudinal direction. Thereby, it permits an increase of total number and total blade-surface area of the assembled fan blades 12′.
However, there exist several drawbacks of the assembled fan blades 12′ in use. In this assembling manner, total number of the assembled fan blade 12′ disposed on the outer circumference of the fan wheel of the fan wheel 1′ is limited. Inevitably, remained between the upper fan blade 12a and the lower fan blade 12b is a clearance due to failure in adhesion or deviation in alignment for assembling operation. Consequently, it results in not only deteriorating quality but also declining throughput of the fan wheel 1′. Hence, there is a need for a fan wheel to increase total number of the fan blades on the outer circumference of the fan wheel. The present invention intends to provide a fan wheel assembly for connecting at least three hub rings that constitutes first-layer fan blades overlapped second-layer and third-layer fan blades along a longitudinal direction. After assembling, each leading edge of one layer of the fan blades overlaps the other two layers of the fan blades along a longitudinal direction. The overlapped fan blades can increase assembled quality and broaden design of the fan wheel assembly in such a way to mitigate and overcome the above problem.